Remove redundant map reduce view registered_patients

[witash]

The registered_patients map reduce view is redundant. It is almost an exact copy of reports_by_subject — both index data_record reports by their subject's patient/place shortcode.

Maintaining a second, near-identical index over every report is wasteful. The view can be removed and its consumers repointed at reports_by_subject.

reports_by_subject is a strict superset of registered_patients: it emits the same patient_id/place_id keys (plus case_id, patient_uuid, and place_uuid) for the same data_record reports. Every consumer of registered_patients already post-filters the returned docs through registrationUtils.isValidRegistration, which discards error docs, non-registrations, and unconfigured forms — so the extra docs surfaced by reports_by_subject are trimmed back to exactly what registered_patients would have returned.

Two differences need to be handled when switching:

• Key coercion: registered_patients emits String(id) keys; reports_by_subject emits the raw value. To preserve matching for any numeric patient_id/place_id, reports_by_subject should coerce its emitted keys with String().
• Duplicate emits: reports_by_subject emits a key from both the top-level property and doc.fields, so a single report can be returned more than once per key. Consumers must de-duplicate the returned docs by _id (getReportsBySubject in transitions already does this).

View: medic-client/registered_patients

Definition

• Database: medic-client (synced to offline clients)
• Map keys: String(doc.patient_id), String(doc.place_id) (falling back to doc.fields.patient_id / doc.fields.place_id)
• Map values: (none)
• Reduce: None

Usages

#	File	Key/Options Used	Functional Purpose
1	shared-libs/transitions/src/lib/utils.js:165	{ key/keys, include_docs: true }	getRegistrations — fetches registration reports for one or more shortcodes, then filters to valid registrations.
2	api/src/services/export/message-mapper.js:122	{ keys: patientIds, include_docs: true }	Hydrates scheduled-task messages with their patient registrations for the messages export.
3	admin/src/js/services/message-queue.js:135	{ keys: shortcodes, include_docs: true }	Loads patient/place registrations for the admin message-queue view.
4	webapp/src/ts/services/format-data-record.service.ts:41	{ key: shortcode, include_docs: true }	Loads registrations for a report's patient/place when formatting scheduled-task messages for display.

Note: removing the view (and the String() change to reports_by_subject) triggers a one-time view reindex on upgrade.